By Michael Erman (Reuters) -Pharmaceutical companies are due to receive by Thursday the U.S. government’s opening proposal for what are expected to be significant discounts on 10 of its high-cost medicines, an important step in the Medicare health program’s first ever price negotiations. Five Wall Street analysts and two investors told Reuters they expect the negotiations over prices that will go into effect in 2026 to result in cuts ranging from the statutory minimum of 25% to as much as 60% when the final numbers are set in September. The drugmakers and the government are expected to wait un…